The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Known hybrid powertrain architectures include torque-generative devices including internal combustion engines and torque machines that can be mechanically coupled to a transmission device to transfer torque to an output member. Known torque machines transform stored energy to power to generate torque. Known control strategies for operating a hybrid powertrain system include executing power management schemes to achieve preferred targets associated with fuel consumption, emissions, and stored energy usage while meeting operator requests for output torque.
Known power management schemes for controlling operation of hybrid powertrain systems monitor present conditions and generate instantaneous control signals to control actuators of the powertrain system.
One known hybrid powertrain system includes an internal combustion engine coupled to an input member of a two-mode, compound-split, electro-mechanical transmission having an output member operatively coupled to a driveline of a motor vehicle for transferring tractive torque thereto. Torque machines including electric machines operate as motors or generators and can generate and transfer input torque to the transmission independently of a torque input from the internal combustion engine. The electric machines may transform vehicle kinetic energy transferred through the vehicle driveline to electrical energy that is storable in an electrical energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the hybrid powertrain, including controlling transmission range state and gear shifting, controlling the torque-generative devices, and regulating the electrical power interchange among the electrical energy storage device and the electric machines to manage outputs of the transmission, including torque and rotational speed.
Known torque machines, including electric machines, can generate audible noise during operation. One audible noise generated by an electric machine is described as a whistling noise. The audible noise can vary over operating conditions of speed and torque output of the torque machines. The audible noise can be objectionable to an operator. Known methods for managing and attenuating the electric machine noise can include adding noise-damping materials and redesigning the machine, including changing magnet structures and changing bearing designs. The audible noise can be noticed with torque machines used to generate tractive or propulsion torque, as they are used to generate maximum torque outputs over a range of machine speeds.